Richard Taylor, a Potomac lawyer and longtime fund-raiser for President Reagan, was chosen today as the national committeeman for Maryland's Republicans. Taylor won election on the third ballot after pledging to use his influence at the White House to get jobs for blacks in Prince George's County.

Taylor made that promise to Sylvester Vaughns, a black Prince George's Republican, as part of a deal that swung the divided Republican convention to Taylor on the third ballot. Taylor won after Stewart Gold, the wealthy Frederick County fund-raiser, failed by a small margin to gather the votes needed for election.

Vaughns, the fourth candidate in a race that also included longtime Prince George's fund-raiser Gerard F. Holcomb, agreed to swing his three votes in the Prince George's delegation to Taylor after Taylor's promise and after former Prince George's county executive Lawrence J. Hogan told Vaughns he should support Taylor.

Taylor's election represents a victory for the older, more conservative wing of the party. Gold, an active fund-raiser and contributor in the state in recent years--and a former Democrat--is considered a "new kid on the block" by party old-timers.

"I owe my election to Gerry Holcomb, to Larry Hogan, to Sylvester Vaughns and to all the people who worked so hard for me," said Taylor, 54, moments after he was elected. "Larry was a big help. He's been a friend for a long time."

Hogan's intervention was ironic since it was his resignation as the national committeeman last December that set up the bitter and protracted fight for the spot. Hogan resigned after becoming a part-time federal consultant, which made him ineligible to hold the committeeman's post under the Hatch Act.

For years, the national commmitteeman has been merely a figurehead, usually a name politician who took the post in addition to various other political appointments. But now, with the state party strapped for money and needing to recoup some respect after its disastrous performance in last year's statewide elections, the job has taken on added significance--especially in the fund-raising area.

Gold, 41, moved to Maryland six years ago but did not register as a Republican until last year. He appeared to have the votes to win the job in January, when the state's executive committee met to appoint Hogan's successor. But the week of the election it was revealed that Gold once contributed $1,000 to the campaign of Sen. Edward Kennedy (D-Mass). That news caused the executive committee to elect Richard Allen as a caretaker candidate, after three ballots, Gold falling one vote short of victory on the first two.

That set the stage for four months of intense campaigning by Gold, Taylor, who was the Reagan campaign's chief fund-raiser in Maryland in 1980, and Holcomb, a longtime Hogan fund-raiser and friend. This week, Vaughns entered the race after reading an article in a local newspaper that said, "What do you call a Republican in Prince George's County? Answer: A tourist."

Hogan, who received $1,000 campaign contributions from both Gold and Taylor during his unsuccessful U.S. Senate campaign last year, said he advised Vaughns to go with Taylor because, "It's important to have access at the national level. As capable and bright as Stu Gold is, he would be suspect for quite a while until he proved himself."

Gold, who had been furious after his defeat in January, was gracious and smiling after his loss today. "This was the old wing of the party versus the new," he said. "We lost. But look how close we came. We're making progress."